Configure LDP IGP synchronization for OSPF

Updated: June 26, 2026

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Configure Label Distribution Protocol (LDP) Interior Gateway Protocol (IGP) synchronization for OSPF to prevent traffic loss and improve network stability during network changes.

By default, there is no synchronization between LDP and IGPs. Without synchronization, OSPF may forward traffic before LDP label exchange is complete, which can cause blackholing. LDP IGP synchronization ensures OSPF waits for label distribution, resulting in a more stable network.

Before you begin

Log in to the router CLI with appropriate privileges.
Verify OSPF is already configured on the device.

Follow these steps to configure and verify LDP IGP synchronization for OSPF:

Procedure

Configure LDP IGP Synchronization under OSPF:

Example:

Router# configure terminal
Router(config)# router ospf 100
Router(config-ospf)# mpls ldp sync
Router(config-ospf)# area 1 mpls ldp sync
Router(config-ospf)# area 1 interface GigabitEthernet0/4/0/2 mpls ldp sync

LDP IGP synchronization is now active for the selected OSPF scope(s). You can verify configuration with MPLS LDP IGP synchronization show commands.

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